The present invention relates to a wind energy converter having a rotor with a vertical swivelling axis and at least one almost vertical propulsive vane mounted on a rotor arm so as to be able to pivot freely about an almost vertical swivelling axis. A balance weight is connected rigidly to the vane ahead of the vane in the direction of rotation.
Numerous versions of wind energy converters with vertical rotor axes are known. They offer the advantage that they are independent of the direction of the wind and can thus be constructed for relatively low construction costs since there is no need to adjust them to accomodate a change in wind direction. A fundamental disadvantage of this type of wind energy converter is that the air-flow angle of the fluctuates between a maximum and a minimum value during each revolution of the rotor. This change in air-flow angle increases with lower relative velocity values. The relative velocity value is the relationship between the wind velocity and the rotational velocity of the rotor.
Mechanical or other positive control systems that vary the angle of attack of the rotor during each rotation of the rotor so as to match it to the air-flow angle are extremely costly from the point of view of their mechanics and require a relatively large amount of energy; in addition, the particular wind direction has to be considered with this control system.
Rigid installation of the vanes on the rotor arms, which thus dispenses with adjustment of the angle of attack to the varying air-flow angle leads to a considerable loss of efficiency of the wind energy converter, since the greatest possible propulsive force on the vane can only be achieved if the angle of attack for the air-flow angle that is effective at any particular moment is at the optimum value. Assymetrical vane airfoil sections that result in a higher propulsive force and thus greater rotor efficiency cannot be used in the range of small relative velocity values since the airflow breaks down completely with large changes in the air-flow angle. For this reason, up to now it has only been possible to use symmetrical airfoils in these ranges, although these are of very low efficiency. Even with these, in the range of the smaller to medium relative velocity values there is still the disadvantage that the change in the air-flow angle will lead in part to separation of the airflow and thus to increase flow resistance during partially diminishing propulsion, which means that the overall efficiency of the wind energy converter will be greatly reduced.
In a known wind energy converter of the kind described in the introduction hereto (DE-AS No. 26 02 380) the vanes are supported on the rotor arms so as to be able to swivel freely and can thus adapt to the constantly changing air-flow angle during every rotation of the rotor. Since the swivelling axis of the vane lies approximately on the leading edge of the vane and thus in front of the centre of gravity of the vane, a balance weight is provided ahead of the swivelling axis, and this offsets the effect of centrifugal force; the swivelling axis lies at the overall centre of gravity of the mass of the body that consists of the vane and the balance weight.
In this known wind energy converter the centrifugal force that is dependent on the rotational speed has no effect on the angle of attack of the vane; the angle of attack changes only under the influence of the flow forces that are effective to a value that results, however, in no optimal propulsive force and thus no favourable degree of efficiency. For this reason, the vane of this known wind energy converter can only be built with symmetrical airfoil sections, and this results in a very low degree of efficiency.
For this reason, it is the task of the present invention to so configure a wind energy converter of the type described in the introduction hereto that it will start to rotate on its own, and that a good degree of efficiency will be achieved, in particular at low and medium relative velocity values.